Pharmacokinetics of L-arginine during chronic administration to patients with hypercholesterolaemia

1999 ◽  
Vol 96 (2) ◽  
pp. 199-207 ◽  
Author(s):  
Oranee TANGPHAO ◽  
Stephan CHALON ◽  
Heitor MORENO ◽  
Brian B. HOFFMAN ◽  
Terrence F. BLASCHKE
Keyword(s):  
Nitric Oxide ◽  
Animal Studies ◽  
Peak Plasma ◽  
Plasma Concentrations ◽  
Area Under The Curve ◽  
Chronic Administration ◽  
Pharmacokinetic Studies ◽  
Acute Administration ◽  
Term Administration ◽  
Endothelial Nitric Oxide

Acute administration of L-arginine, the precursor of endothelial nitric oxide, has been shown to improve endothelial function in hypercholesterolaemic rabbits and humans. Animal studies suggest that this beneficial effect, which is thought to be related to the increased availability of nitric oxide, may not be sustained during chronic oral administration. Pharmacokinetic alterations may contribute to this observation. The present study was designed to examine the disposition of L-arginine in hypercholesterolaemic subjects during long-term administration. Plasma L-arginine concentrations were determined by HPLC in 10 patients (eight women and two men; mean age 46±16 years) after an intravenous dose of 10 or 30 g and an oral dose of 5 or 7 g. Pharmacokinetic studies were performed at regular intervals (4 weeks) during a 12-week period of oral L-arginine administration (14–21 g/day). The average plasma L-arginine concentrations before (baseline) and during administration were 16.1±1.2 and 22.5±1.3 μg/ml respectively (P< 0.05). Plasma concentrations of L-arginine remained above baseline throughout weeks 2–12. The L-arginine exposure, expressed as a normalized area-under-the-curve for 8 h (AUC0–8) after oral or intravenous doses during the first visit, was 894.4±118.7 and 1837.8±157.0 units respectively. There were no significant changes in peak plasma L-arginine concentrations or in the AUC0–8 after oral and intravenous doses during subsequent visits (P> 0.05). The mean non-renal clearance of L-arginine during the four visits remained constant. Knowledge of the pharmacokinetics of L-arginine may be useful in the design of clinical trials involving this agent, as well as in the interpretation of the pharmacodynamics of this important precursor of nitric oxide.

Clinical and Pharmacokinetic Evaluation of Long-Term Therapy With Didanosine in Children with HIV Infection

PEDIATRICS ◽  
1994 ◽  
Vol 94 (5) ◽  
pp. 724-731 ◽  
Author(s):  
Brigitta U. Mueller ◽  
Karina M. Butler ◽  
Vicki L. Stocker ◽  
Frank M. Balis ◽  
Philip A. Pizzo ◽  
...  
Keyword(s):  
Hiv Infection ◽  
Area Under The Curve ◽  
Chronic Administration ◽  
Cd4 Count ◽  
Term Therapy ◽  
Short Term ◽  
Apparent Relationship ◽  
Term Administration ◽  
Long Term Therapy

Background. Didanosine has demonstrated promising antiviral activity and a tolerable toxicity profile in short term studies. We describe a cohort of HIV-infected children who were treated for a prolonged period of time with didanosine. Methods. Children (6 months to 18 years of age) with symptomatic HIV infection or an absolute CD4 count &lt; 0.5 x 109 cells/L, received oral didanosine at doses between 20 mg/m2 to 180 mg/m2 every 8 hours. Clinical, immunological, and virological parameters were assessed at least every 2 months. The pharmacokinetics of didanosine were evaluated in 85 patients. Results. Previously untreated children (n = 51) and children who had received prior antiretroviral therapy (n = 52) were enrolled in the study (median time on study 22.6 months; range 2 to 48). The long-term administration of didanosine was well tolerated and no new toxicities were observed. The absolute CD4 count increased by ≥ .05 x 109 cells/L in 28 of 87 (32%) of patients after 6 months of therapy. Responses were also sustained in 41% of these children after 3 years of therapy. Children entering the study with a CD4 count &gt;0.1 x 109 cells/L (n = 51) had a marked survival advantage (P = .00002) with an estimated survival probability after 3 years of 80% compared to 39% for children with lower CD4 counts. Although the area under the curve of didanosine increased proportionally with the dose, there was considerable interpatient variability at each dose level. There was no apparent relationship between surrogate markers of clinical outcome and plasma drug concentration. Conclusions. Didanosine was well tolerated with chronic administration, and toxicities were uncommon and usually reversible. In 41% of patients, the CD4 count increased and was maintained at the higher level even after years of treatment.

scholarly journals The Effects of Oral l-Arginine and l-Citrulline Supplementation on Blood Pressure

Nutrients ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1679 ◽  
Author(s):  
David Khalaf ◽  
Marcus Krüger ◽  
Markus Wehland ◽  
Manfred Infanger ◽  
Daniela Grimm
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Animal Studies ◽  
Current Data ◽  
No Production ◽  
First Pass Metabolism ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide ◽  
Antihypertensive Properties ◽  
Pass Metabolism

Nitric oxide (NO) is a well-known vasodilator produced by the vascular endothelium via the enzyme endothelial nitric oxide synthase (eNOS). The inadequate production of NO has been linked to elevated blood pressure (BP) in both human and animal studies, and might be due to substrate inaccessibility. This review aimed to investigate whether oral administration of the amino acids l-arginine (Arg) and l-citrulline (Cit), which are potential substrates for eNOS, could effectively reduce BP by increasing NO production. Both Arg and Cit are effective at increasing plasma Arg. Cit is approximately twice as potent, which is most likely due to a lower first-pass metabolism. The current data suggest that oral Arg supplementation can lower BP by 5.39/2.66 mmHg, which is an effect that is comparable with diet changes and exercise implementation. The antihypertensive properties of Cit are more questionable, but are likely in the range of 4.1/2.08 to 7.54/3.77 mmHg. The exact mechanism by which Cit and Arg exert their effect is not fully understood, as normal plasma Arg concentration greatly exceeds the Michaelis constant (Km) of eNOS. Thus, elevated plasma Arg concentrations would not be expected to increase endogenous NO production significantly, but have nonetheless been observed in other studies. This phenomenon is known as the “l-arginine paradox”.

Role of AT1 receptors in the renal papillary effects of acute and chronic nitric oxide inhibition

1998 ◽  
Vol 274 (3) ◽  
pp. R760-R766 ◽  
Author(s):  
M. Clara Ortíz ◽  
Lourdes A. Fortepiani ◽  
Francisco M. Ruiz-Marcos ◽  
Noemí M. Atucha ◽  
Joaquín García-Estañ
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Angiotensin Ii ◽  
Chronic Administration ◽  
Acute Administration ◽  
Synthesis Inhibitor ◽  
Renal Vasoconstriction ◽  
Oxide Inhibition ◽  
Stimulation Of

Nitric oxide (NO) is a vasodilator substance controlling renal papillary blood flow (PBF) in the rat. In this study we have evaluated the role of AT1 angiotensin II receptors as modulators of the whole kidney and papillary vasoconstrictor effects induced by the acute or chronic inhibition of NO synthesis. Experiments have been performed in anesthetized, euvolemic Munich-Wistar rats prepared for the study of renal blood flow (RBF) and PBF. In normal rats, acute administration of the NO synthesis inhibitor N ω-nitro-l-arginine methyl ester (l-NAME) increased mean arterial pressure (MAP) and decreased RBF and PBF. Either acute or chronic treatment with the AT1 receptor blocker losartan did not modify the decreases in RBF or PBF secondary to l-NAME. In animals made hypertensive by chronic inhibition of NO, basal MAP was higher, whereas RBF and PBF were lower than in the controls. In these animals, acute or chronic administration of losartan decreased MAP and increased both RBF and PBF significantly. These results indicate that, under normal conditions, the decreases in RBF or PBF induced by the acute inhibition of NO synthesis are not modulated by AT1-receptor stimulation. However, the arterial hypertension, renal vasoconstriction, and reduced PBF present in chronic NO-deficient hypertensive rats is partially due to the effects of angiotensin II, via stimulation of AT1-receptors.

The disposition of TCNU (tauromustine) in human malignant glioma: pharmacokinetic studies and clinical implications

1990 ◽  
Vol 72 (5) ◽  
pp. 721-725 ◽  
Author(s):  
Ian R. Whittle ◽  
Janet S. MacPherson ◽  
J. Douglas Miller ◽  
John F. Smyth
Keyword(s):  
Malignant Glioma ◽  
High Performance ◽  
Peak Plasma ◽  
Linear Regression Analysis ◽  
Plasma Concentrations ◽  
Tissue Level ◽  
Pharmacokinetic Studies ◽  
Tissue Concentrations ◽  
Content Type ◽  
Chromatography Analysis

✓ Tauromustine (TCNU), 130 mg/sq m, was administered intraoperatively by nasogastric tube to 10 patients with malignant glioma (seven glioblastomas and three anaplastic astrocytomas). High-performance liquid chromatography analysis of 32 tumor specimens for TCNU revealed that tissue concentrations ranged from 0 to 554 ng/gm; TCNU was not detected in necrotic regions of the tumor. Levels of TCNU in brain adjacent to tumor were similar to those recorded within the gliomas (range 0 to 635 ng/gm). The variability in the tissue level of TCNU was partly attributable to variable absorption of the drug, since peak plasma TCNU levels ranged from 164 to 3333 ng/ml. There were close quantitative and temporal relationships between the times of peak plasma levels (median 456 ng/ml at 45 minutes after administration), peak tumor levels (median 250 ng/gm tissue at 55 minutes), and brain adjacent to tumor levels (median 256 ng/gm tissue at 50 minutes). Linear regression analysis of the ratio between tissue and plasma TCNU levels at particular times after drug administration suggest that plasma concentrations can be used to estimate tissue concentrations. This study demonstrates that TCNU enters malignant glioma. In view of the activity of TCNU against a range of tumors, a full clinical evaluation of this new nitrosourea in malignant glioma seems justified.

scholarly journals Potential mechanisms for the effects of far-infrared on the cardiovascular system – a review

VASA ◽  
2019 ◽  
Vol 48 (4) ◽  
pp. 303-312 ◽  
Author(s):  
Richard Shemilt ◽  
Hala Bagabir ◽  
Chim Lang ◽  
Faisel Khan
Keyword(s):  
Nitric Oxide ◽  
Cardiovascular System ◽  
Animal Studies ◽  
Cardiovascular Health ◽  
Far Infrared ◽  
Therapeutic Effects ◽  
Beneficial Effects ◽  
Wide Range ◽  
Shock Proteins ◽  
Endothelial Nitric Oxide

Abstract. Far-infrared (FIR) is a form of thermal radiation, which may have beneficial effects on cardiovascular health. Clinical studies suggest that FIR irradiation may have therapeutic effects in heart failure, myocardial ischaemia and may improve flow and survival of arteriovenous fistula. Animal studies have suggested a wide range of potential mechanisms involving endothelial nitric oxide synthase and nitric oxide bioavailability, oxidative stress, heat shock proteins and endothelial precursor cells. However, the exact cellular and molecular mechanism of FIR on the cardiovascular system remains elusive. The purpose of this review is to discuss the current literature, focusing on mechanistic studies involving the cardiovascular system, and with a view to highlighting areas for future investigation.

Pharmacokinetics and investigation of optimal dose ertapenem in intermittent hemodialysis patients

2018 ◽  
Vol 34 (10) ◽  
pp. 1766-1772 ◽  
Author(s):  
Lama M Hsaiky ◽  
Francine D Salinitri ◽  
Judy Wong ◽  
Sin-Ling T Jennings ◽  
Neha H Desai ◽  
...  
Keyword(s):  
Half Life ◽  
Plasma Concentrations ◽  
Area Under The Curve ◽  
Optimal Dose ◽  
Hemodialysis Patients ◽  
Pharmacokinetic Parameters ◽  
Intermittent Hemodialysis ◽  
Pharmacokinetic Studies ◽  
Open Label ◽  
Serious Adverse Events

Abstract Background Previous pharmacokinetic studies demonstrated an increase in serum ertapenem concentrations with decreasing kidney function, including patients receiving renal replacement therapy. This study evaluated the pharmacokinetic parameters of ertapenem in patients receiving hemodialysis. Methods This prospective, single-center, open-label study examined the pharmacokinetics of a single intravenous (IV) dose of ertapenem 1 g in seven hospitalized noninfected patients undergoing hemodialysis. Blood samples were collected prior to ertapenem administration and at 0.5, 1, 2, 6, 12 and 48 hours (h) after administration. Ertapenem concentrations were determined by validated liquid chromatography mass spectrometry assay. Results Following an IV bolus of 1 g ertapenem, plasma concentrations declined relatively slowly with a mean ±standard deviation (SD) elimination half-life of 19.3 ±6.6 h. Plasma concentrations were similar in all subjects, with maximum mean plasma concentration observed of 343±48 µg/mL postdose. The mean ±SD values for systemic plasma clearance (CL) and volume of distribution at steady state (Vss) were 2±0.5 mL/min and 3295±1187 mL, respectively. The area under the curve for 0 h–∞ (AUCinf) was 7494 ±1424 h•µg/mL. No gender effect was observed and no serious adverse events were reported. Conclusions Ertapenem half-life was prolonged in hemodialysis patients. Considering the nonrenal clearance and the expected 70% removal with high-efficacy hemodialysis, the dose of 1 g ertapenem, three times weekly, after hemodialysis may produce pharmacodynamically sufficient exposure for potential antimicrobial efficacy. Further studies are warranted to assess the clinical efficacy and safety of this dose with prolonged duration of therapy.

Glucuronidation and its effect on the bioactivity of amentoflavone, a biflavonoid from Ginkgo biloba leaves

2020 ◽  
Author(s):  
Lili Gan ◽  
Jiating Ma ◽  
Guoquan You ◽  
Jinxia Mai ◽  
Zhaoyu Wang ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Anticancer Activity ◽  
Ginkgo Biloba ◽  
Metabolic Profile ◽  
Plasma Concentrations ◽  
Area Under The Curve ◽  
Pharmacokinetic Studies ◽  
Significant Difference ◽  
Dietary Flavonoid ◽  
U251 Cells

Abstract Objectives Ginkgo biloba leaves contain amentoflavone (AMF), a dietary flavonoid that possesses antioxidant and anticancer activity. Flavonoids are extensively subjected to glucuronidation. This study aimed to determine the metabolic profile of AMF and the effect of glucuronidation on AMF bioactivity. Methods A pharmacokinetic study was conducted to determine the plasma concentrations of AMF and its metabolites. The metabolic profile of AMF was elucidated using different species of microsomes. The antioxidant activity of AMF metabolites was determined using DPPH/ABTS radical and nitric oxide assays. The anticancer activity of AMF metabolites was evaluated in U87MG/U251 cells. Key findings Pharmacokinetic studies indicated that the oral bioavailability of AMF was 0.06 ± 0.04%, and the area under the curve of the glucuronidated AMF metabolites (410.938 ± 62.219 ng/ml h) was significantly higher than that of AMF (194.509 ± 16.915 ng/ml h). UGT1A1 and UGT1A3 greatly metabolized AMF. No significant difference was observed in the antioxidant activity between AMF and its metabolites. The anticancer activity of AMF metabolites significantly decreased. Conclusions A low AMF bioavailability was due to extensive glucuronidation, which was mediated by UGT1A1 and UGT1A3. Glucuronidated AMF metabolites had the same antioxidant but had a lower anticancer activity than that of AMF.

scholarly journals Pharmacokinetics and Safety of Mitragynine in Beagle Dogs

Planta Medica ◽  
2020 ◽  
Vol 86 (17) ◽  
pp. 1278-1285 ◽  
Author(s):  
Elizabeth A. Maxwell ◽  
Tamara I. King ◽  
Shyam H. Kamble ◽  
Kanumuri Siva Rama Raju ◽  
Erin C. Berthold ◽  
...  
Keyword(s):  
Peak Plasma ◽  
Plasma Concentrations ◽  
Compartmental Analysis ◽  
Ultra Performance Liquid Chromatography ◽  
Volume Of Distribution ◽  
Pharmacokinetic Studies ◽  
Beagle Dogs ◽  
Limit Of Quantification ◽  
Significant Information ◽  
Pharmacokinetic Properties

AbstractMitragynine is the most abundant psychoactive alkaloid derived from the leaves of Mitragyna speciosa (kratom), a tropical plant indigenous to regions of Southeast Asia. Mitragynine displays a moderate affinity to opioid receptors, and kratom is often self-prescribed to treat pain and/or opioid addiction. The purpose of this study was to investigate the safety and pharmacokinetic properties of mitragynine in the dog. Single dose oral (5 mg/kg) and intravenous (0.1 mg/kg) pharmacokinetic studies of mitragynine were performed in female beagle dogs. The plasma concentrations of mitragynine were measured using ultra-performance liquid chromatography coupled with a tandem mass spectrometer, and the pharmacokinetic properties were analyzed using non-compartmental analysis. Following intravenous administration, mitragynine showed a large volume of distribution (Vd, 6.3 ± 0.6 L/kg) and high clearance (Cl, 1.8 ± 0.4 L/h/kg). Following oral mitragynine dosing, first peak plasma (Cmax, 278.0 ± 47.4 ng/mL) concentrations were observed within 0.5 h. A potent mu-opioid receptor agonist and active metabolite of mitragynine, 7-hydroxymitragynine, was also observed with a Cmax of 31.5 ± 3.3 ng/mL and a Tmax of 1.7 ± 0.6 h in orally dosed dogs while its plasma concentrations were below the lower limit of quantification (1 ng/mL) for the intravenous study. The absolute oral bioavailability of mitragynine was 69.6%. Administration of mitragynine was well tolerated, although mild sedation and anxiolytic effects were observed. These results provide the first detailed pharmacokinetic information for mitragynine in a non-rodent species (the dog) and therefore also provide significant information for allometric scaling and dose predictions when designing clinical studies.

scholarly journals Pharmacokinetics of Posaconazole Suspension in Lung Transplant Patients with and without Cystic Fibrosis

2016 ◽  
Vol 60 (6) ◽  
pp. 3558-3562 ◽  
Author(s):  
Hongfei Zhang ◽  
M. Hong Nguyen ◽  
Cornelius J. Clancy ◽  
Rujuta Joshi ◽  
Wenchen Zhao ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Lung Transplant ◽  
Fungal Infections ◽  
Plasma Concentrations ◽  
Treatment Strategies ◽  
Area Under The Curve ◽  
Therapeutic Drug ◽  
Pharmacokinetic Studies ◽  
Pharmacokinetic Data ◽  
Average Dose

Invasive fungal infections (IFIs) are common among lung transplant recipients (LTRs). Posaconazole is an important antifungal agent for both prophylaxis and treatment of IFIs; however, detailed pharmacokinetic data are limited among LTRs, particularly those with cystic fibrosis (CF). Our objective was to conduct a pharmacokinetic study of posaconazole oral suspension among LTRs, with particular attention to patients with CF. We enrolled 20 LTRs, 7 with CF and 13 with other underlying lung diseases. Average daily doses in CF and non-CF patients were 829 and 862 mg, respectively. After ≥5 days of treatment, only 4 patients had average plasma concentrations of >0.7 μg/ml. Average steady-state plasma concentrations were 61% lower in CF patients (0.233 μg/ml) than in non-CF LTRs (0.594 μg/ml;P= 0.03). The average dose-normalized plasma area-under-the-curve (AUC) values were also lower in CF (0.007 h·μg/ml) than in non-CF LTRs (0.02 h·μg/ml;P= 0.02). The weight-normalized apparent oral clearance values were 2.51 and 0.74 liters/h/kg among CF and non-CF LTRs, respectively (P= 0.005). Despite significant interpatient variability, plasma trough concentrations were strongly correlated with posaconazole AUC across all LTRs (r2= 0.95,P< 0.0001). Taken together, our study highlights a critical need to incorporate new formulations of posaconazole into prophylaxis and treatment strategies for LTRs, particularly those with CF. Future pharmacokinetic studies of both tablet and intravenous formulations must consider LTR-specific factors and incorporate a therapeutic drug monitoring plan in this patient population.

The Clinical Pharmacokinetics of Quinapril

Angiology ◽  
1989 ◽  
Vol 40 (4_part_2) ◽  
pp. 351-359 ◽  
Author(s):  
Stephen C. Olson ◽  
Ann Marie Horvath ◽  
Barbara M. Michniewicz ◽  
Allen J. Sedman ◽  
Wayne A. Colburn ◽  
...  
Keyword(s):  
Half Life ◽  
Peak Plasma ◽  
Dose Range ◽  
Plasma Concentrations ◽  
Area Under The Curve ◽  
Clinical Pharmacokinetics ◽  
Q 61 ◽  
Dose Proportional

Quinapril (Q) and quinaprilat (QT) pharmacokinetics are dose pro portional following single oral 2.5- to 80-mg Q doses. Q absorption and hy drolysis to QT is rapid with peak Q and QT concentrations occurring one and two hours postdose, respectively. Peak plasma QT concentrations were approximately fourfold higher than those of Q (923 vs 207 ng/mL follow ing 40-mg Q). Dose-proportional QT area under the curve and dose-inde pendent percent of dose excreted in urine as QT demonstrate that the ex tent of Q conversion to QT is con stant over the dose range studied. Q and QT were eliminated from plasma with apparent half-lives of 0.8 and 1.9 hours and apparent plasma clear ances of 1,850 and 220 mL/min, re spectively, over the 2.5- to 80-mg dose range. Following oral 14C-Q, 61% and 37% of radiolabel was recovered in urine and feces, respectively. Q plus QT accounted for 46% of radioactiv ity circulating in plasma and 56% of that excreted in urine. Metabolism to compounds other than QT is not extensive. Two diketo piperazine metabolites of Q have been identified in plasma and urine, with approximately 6% of an admin istered dose excreted in urine as each of these metabolites. Peak plasma concentrations of these metabolites are similar to that of Q, and each is eliminated rapidly with a half-life of approximately one hour. Urinary ex cretion profiles indicate the presence of other minor metabolites. In summary, the absorption of Q and conversion to QT is rapid and dose-proportional, subsequent clear ance of both Q and QT is independ ent of dose, and metabolism to compounds other than QT is not ex tensive.

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